Feat: update VSCode extension with compound assignment and shift operators

Add compound assignment operators (+=, -=, *=, /=, %=, &=, |=, ^=,
<<=, >>=) and shift operators (<<, >>) to the tmLanguage syntax
highlighting grammar. Patterns are ordered longest-first to prevent
shorter tokens from shadowing multi-character operators. Also update
fibonacci example to use += compound assignment.

examples/fibonacci.flx

@@ -16,7 +16,7 @@ fn fibonacci_iter(n: u8) -> u64 {
         a = b;
         b = temp;
 
-        counter = counter + 1;
+        counter += 1;
     }
 
     return a;